Why (some) sleepy brains get grumpy

Some people are cool not getting enough sleep. I am, however, not one of those. After almost two years of sleep deprivation I can say I am close to becoming the grumpy dwarf from Snow White. And up until now, I didn’t have a reason to justify why me and not others. But Sahil Bajaj and William Killgore ¹, have given me hope. Their study on the anatomy of three different brain networks and mood after sleep deprivation led them to conclude that there is a relationship between white matter and moodiness. Their study focused on the default mode network (DMN), which may be related to dreaming and help consolidate memories while sleeping, while the central executive network (CEN) is action-oriented. The third network, the scientists looked at was the salience network, supposed to be the one mediating between DMN and CEN and putting together emotional and sensory stimuli.

Since interaction among these three networks has been associated with neurological diseases, it seemed like a good place to start looking. 45 people took part in the study, diffusion tension imaging inside an MRI produced high resolution anatomical data before 24h-sleep deprivation. During this time, their mood was assessed every hour between 7:15 p.m. and 11:15 a.m. the following morning. The analysis of the data did not show any correlation between specific networks and bad mood, but id did find a consistent one between compactness of white matter (nerve fibres,mostly) and mood. Namely, the more compacted the white matter, the less affected the people’s mood by the lack of sleep. Problems to the conclusions of the study: potentially, as disclosed by the researchers, the technique has resolution limitations, and there might be an underlying cause that they couldn’t pick up with their MRI machine. On the other hand, correlation doesn’t mean causation, which means that even if people more resilient to sleep deprivation show more compacted white matter, it doesn’t mean that this compactness is the reason for this resilience. It could very well be a consequence or just a correlate. So, I still cannot tell why I am sooooo moody when I don’t get my beauty sleep, but at least I know that my white matter is, unfortunately, not so compacted. I keep on hoping that more research will bring me the answer, and further down the line something to see the sunshine without getting enough shuteye. Until then…good night!